What is the total usable fuel capacity of the aircraft?

The total usable fuel capacity of an aircraft is an essential specification that directly impacts flight planning, weight calculations, and overall aircraft performance. In this case, the correct answer indicates that the aircraft can safely operate with 40 gallons of fuel that are usable for flight.

Understanding usable fuel capacity is crucial for pilots because it informs them how much fuel is available for the duration of the flight and helps avoid potential issues such as running out of fuel mid-flight. It's important to differentiate between total fuel capacity and usable fuel capacity, as some of the fuel may be unusable due to design considerations, such as fuel system geometry or the need to maintain a reserve for safety reasons.

The other fuel capacities provided in the options either exceed or fall short of the actual usable capacity of the aircraft in question. Choosing 40 gallons reflects an awareness of the balance between safety, operational requirements, and aircraft performance characteristics. By knowing that figure, pilots can effectively plan fuel stops, calculate weight and balance, and ensure they comply with regulatory requirements pertaining to fuel reserves.